Dynamic pumps are most widely used for high-pressure applications. These pumps have a high efficiency compared to positive displacement pumps. There are many types of dynamic pumps, and an axial flow pump is one of them. In the previous article, we discussed radial flow centrifugal pumps. This article explains the axial flow pump working, types, and applications.
What is Axial flow Pump?
An axial flow pump is a type of centrifugal pump in which the fluid enters and exits the pump in a parallel direction to the impeller. It has a suction parallel to the impeller.
An axial flow pump doesn’t change the flow direction of the fluid. It has an impeller inside the pipe. This pump has three to four blades that are installed on the impeller.
The pump blades are designed in such a way that the pump discharges the water axially in a parallel direction to the impeller, not perpendicular. The parallel alignment of the impeller blades creates a very low pressure when pumping water.
These dynamic pumps can generate high flow rates, up to hundreds of thousands of gallons per minute. It is sometimes called a propeller pump because the axial impeller is similar to a ship’s propeller. In some configurations, the flow rate and head can be adjusted by changing the pitch of the impeller blades.
Axial flow pumps are most usually used in applications where the low head and high flow rates supplies are required, such as in water treatment, flood control, and irrigation applications. These types of pumps are also employed in the marine industries to pump bilge and ballast transfer operations.
They are usually more efficient than other types of pumps at a high flow rate. However, the performance of these pumps reduces at low flow rates. Axial flow pumps have large sizes and are costly.
Working Principle of Axial Flow Pump
In the axial flow pump, the impeller blades guide the fluid axially. In this pump, the pressure generates by passing the fluid over the impeller vanes. In these dynamic pumps, the impeller blades have an airfoil section through which fluid runs and create pressure.
The liquid is forced in the direction of the axis of rotation of the impeller. That’s why, the fluid particles do not transform their radial position as they flow through the pump. This permits the liquid to flow axially into the impeller and to exit the fluid approximately axially. The propeller of the axial pump is driven by an electric motor.
The required power increases with a decreasing flow rate, and the maximum power is drawn at a zero-flow rate. While in the case of the centrifugal radial pump, this feature is the opposite, in which power requirements increase with increasing the flow rate.
Compared to conventional centrifugal or radial pumps, axial pumps can pump up to three times more liquids with a delivery head of fewer than 4 meters. By changing the propeller pitch, you can easily set these dynamic pumps to run with maximum efficiency at high or low pressure and low/high pressure.
The axial flow pump generally has a low head than radial pumps but can generate higher currents. Axial flow pumps can only produce heads of 10 to 20 feet. This is lower as compared to other types of centrifugal pumps.
How to select an Axial Pump
If you want to buy an axial flow pump, then keep in mind the following specifications to choose the best suitable pump:
- Flow Rate: The speed at which liquids flow by the pump (gallons/minute (GPM)) is known as the flow rate. To choose a pump, you must know the fluid flow rate that you want to pump because the nominal capacity and pump flow rate must match for a smooth process.
- Pressure: Pressure is another significant factor that you need to keep in mind for choosing a pump. Choose a pump that may handle your fluid pressure according to your desire.
- Head: It is a height from the inlet area to the discharge area. It describes in feet or meters. Choose a pump that can pump fluid up to your desired head.
- Net Positive Suction Head (NPSH): The pressure difference between the pump inlet heads and the vapor head is known as NPSH. This term calculates to prevent cavitation issues.
- Output power: The absolute power generated by the pump is known as output power. Choose an axial flow pump according to your desired output power.
- Input power: the energy required to run the pump.
- Efficiency: It is a ratio of input power to output power. Efficiency defines the amount of input energy used for pumping. It is another important factor that must be kept in mind for choosing a pump.
Applications of Axial Pump
- Chemical processing: Axial flow pumps are used in the chemical processing plant to transfer chemicals and other liquids by different phases of the production process.
- Water treatment: They are employed in the water treatment system to pump water through various stages of the treatment process.
- Irrigation: Axial flow pumps are most usually used in irrigation systems to transfer a large volume of water from a source, such as a reservoir or a river, to crops.
- Cooling systems: These types of centrifugal pumps are utilized in cooling systems, like HVAC systems and power plants, to circulate water and remove heat from the system.
- Marine industry: They are employed in the marine industries for firefighting operations, bilge pumping, and ballast transfer.
- Hydroelectric power generation systems: These are employed in the hydroelectric power generation system to pump water by turbines.
- Oil and gas industry: They are used in the oil and gas industries to transfer natural gas, crude oil, and other fluids.
- Flood control systems: Axial flow pumps are employed in flood control systems to pump a large amount of water from one location to another.
Advantages and disadvantages of Axial Pumps
Advantages of Axial flow Pumps
- The main advantage of axial pumps is that they have a relatively low head and a relatively high flow rate.
- These dynamic pumps are ideal for l high flow rate and low head.
- With axial pumps, the effects of fluid turning are less severe.
- Axial pumps can easily be set up for low flow and high head for high-efficiency operation.
- Of the many conventional pumps, these pumps are the smallest.
- The small size makes it easy to use and handle.
Disadvantages of Axial flow Pumps
- These pumps have a high cost.
- These pumps can’t control liquids having high viscosity.
- They are not best for applications that require a high head.
Difference between Axial Pump and Radial Centrifugal Pump
|Parameter||Radial Flow Pump||Axial Flow Pump|
|Efficiency||Medium to high||High|
|Pressure Range||High pressure||Low pressure|
|Operating Range||Low to high flow rate||High flow rate|
|Cost||Low cost||High cost|
|Impeller Type||Curved blades||Propeller-like|
|Size||Small to large||Large|
|NPSH||More required||Less required|
|Cavitation||More likely||Less likely|
|Applications||Oil and gas, water supply, chemical processing, and HVAC||Hydroelectric, marine, cooling, flood control, and irrigation|
What are axial pumps used for?
Axial flow pumps are most usually used in applications where the low head and high flow rates supplies are required, such as in water treatment, flood control, and irrigation applications.
What are the components of Axial Pump?
- Suction port
- Discharge port